fix for qrewrite failing with dataset wildcards

* qrewrite was creating a DASQuery({spec: dataset.name='<PK>', ...})
    which was not passing wildcard validation (since wildcard check do not need dbsmanager to be passed).
* the simple fix is to pass a valid dataset name instead (e.g. /a/b/c)
Merge pull request #4076 from dmwm/fix_qrewrite_wildcard

fix for qrewrite failing with dataset wildcards (in testbed, needs patching)